Turbine engines, and particularly gas or combustion turbine engines, are rotary engines that extract energy from a flow of combusted gases passing through the engine onto a multitude of turbine blades. Gas turbine engines have been used for land and nautical locomotion and power generation, but are most commonly used for aeronautical applications such as for aircraft, including helicopters. In aircraft, gas turbine engines are used for propulsion of the aircraft. In terrestrial applications, turbine engines are often used for power generation.
Gas turbine engines for aircraft are designed to operate at high temperatures to maximize engine efficiency, so cooling of certain engine components, such as the high pressure turbine and the low pressure turbine, may be necessary. Typically, cooling is accomplished by ducting cooler air from the high and/or low pressure compressors to the engine components which require cooling. Temperatures in the high pressure turbine are around 1000° C. to 2000° C. and the cooling air from the compressor is around 500° C. to 700° C. While the compressor air is a high temperature, it is cooler relative to the turbine air, and may be used to cool the turbine.
Particles, such as dirt, dust, sand, and other environmental contaminants, in the cooling air can cause a loss of cooling and reduced operational time or “time-on-wing” for the aircraft environment. For example, particles supplied to the turbine blades can clog, obstruct, or coat the flow passages and surfaces of the blades, which can reduce the lifespan of the turbine. This problem is exacerbated in certain operating environments around the globe where turbine engines are exposed to significant amounts of airborne particles.
In geographic regions of the world that are in proximity to desert environments, this airborne particulate is often fine grain sand. Fine sand particulate is easily ingested into the engine core through the gas turbine inlet, and is subsequently carried into the cooling system. Once in the cooling system, fine sand particulate has a propensity to deposit on high temperature surfaces, such as those found in the turbine guide vanes aft of the combustor, and will accumulate over time to block the flow of cooling air or foul small holes, such as the film cooling holes, which leads to a loss of cooling effectiveness that increases component metal temperatures and thus can negatively impact the durability of the engine component. Fine sand accumulation is particularly prevalent when impingement cooling systems are employed through the use of an impingement baffle, or insert, in which the cooling air is directed to impinge in small jets on the internal surface of the turbine guide vanes surface adjacent to the hot gas path air to increase the cooling effectiveness.